H. pylori is a widespread, spiral-shaped, flagellated Gram-negative bacterium usually infects the gastric mucosa.Its seropositivity increases with age as it affects about eighty percent of the middle-aged adults in the developing countries and about twenty-five to fifty percent in the western populations.The relation between infection and autoimmune diseases has been previously investigated. Many Gram-negative bacteria as salmonella, shigella, and chlamydia were confirmed to be associated with the development of reactive arthritis.These bacteria have been found to stimulate the host immune response due to the presence of lipopolysaccharides and other antigenic molecules that can cause inflammation.It has been previously hypothesized that H. pylori can induce such immune host response through many mechanisms as the molecular mimicry and antigenic similarity, disruption of the tolerogenic immune response, and activation of the polyclonal lymphocytes leading ultimately to the imbalance between T regulatory/Th17 cells in addition to the induction of autoantibody production
